Method for charging refrigerant blend

ABSTRACT

The present invention provides a method for charging a refrigerant blend characterized in that, in case of employing as refrigerant a non-azeotropic blend comprising 23% by weight of difluoromethane, 25% by weight of pentafluoroethane and 52% of 1,1,1,2-tetrafluoroethane, composition change associated with transfer is allow to fall within the permissible range of performance of the non-azeotropic refrigerant blend by adjusting a composition of the non-azeotropic blend in a feeding container such as bomb to 23.5-25.0% by weight of difluoromethane, 23.5-25.0% by weight of pentafluoroethane and 50.0-53.0% by weight of 1,1,1,2-tetrafluoroethane followed by discharging the non-azeotropic blend from a liquid phase at 40° C. or less. According to the charging method, composition change associated with transfer of non-azeotropic HFC32/HFC125/HFC134a refrigerant blend may be allowed to fall within the permissible range of performance of refrigerant.

TECHNICAL FIELD

The present invention relates to a method for charging a non-azeotropicrefrigerant blend comprising 23% by weight of difluoromethane, 25% byweight of pentafluoroethane and 52% by weight of1,1,1,2-tetrafluoroethane used as a working fluid for vapor compressionrefrigeration cycle.

BACKGROUND ART

Vapor compression refrigeration cycle to perform cooling and heating offluids by the use of state change of material such as evaporation andcondensation has found a widespread use for applications such as anair-conditioner, refrigerator, hot-water supplier, etc. A variety ofworking fluids which are applied for the vapor compression refrigerationcycle, especially fluorocarbon refrigerants, have been developed andpractically used. Among the fluids, HCFC22 (monochlorodifluoromethane)is widely used as a refrigerant in a heating and cooling system forair-conditioning.

However, chlorofluorocarbons were recently found to be responsible forthe destruction of the ozone layer when released into the stratosphereand eventually exert seriously adverse effects on the ecosystemincluding human on the earth. Then, a worldwide agreement calls for therestriction of use and in the future total abolition thereof. Underthese circumstances, there is an urgent demand for developing a newrefrigerant which has no or little potential to cause the problem ofdepleting the ozone layer.

As attempts to make up for insufficient performances of a singlecomponent refrigerant by the use of refrigerant blends, many proposalsfor using non-azeotropic refrigerant blends have recently been raised(e.g., Japanese Unexamined Patent Publication No. 79288/1989, JapaneseExamined Patent Publication No. 55942/1994, and Japanese UnexaminedPatent Publication No. 287688/1991).

A non-azeotropic mixture causes a composition change during phase changesuch as evaporation and condensation, since a component having lowerboiling point is likely to be evaporated and a component having higherboiling point is likely to be condensed. The tendency of compositionchange is pronounced in the case of evaporation, i.e., phase change fromliquid to vapor, and the tendency is particularly pronounced asdifferences of boiling point between components are larger. Therefore,when such a non-azeotropic blend is transferred from one container toanother, it is common practice to discharge it from liquid phase so asnot to arise the phase change. However, even in the case of discharginga refrigerant blend from liquid phase, phase change as much as a fewpercent occurs in the case where the differences in boiling points arelarge between components. This is because discharging the blend causes adecrease of pressure and increase of the gaseous space, resulting inevaporation of lower-boiling-point components from liquid phase. A fewpercent of composition change cause a significant change in performancesof refrigerant, and the change not only results in a decrease incapability and efficiency of the refrigerant, but also adversely affectssafety of refrigerants such as flammability.

In particular, when using as a refrigerant a non-azeotropic blendcomprising 23% by weight of difluoromethane (thereafter referred to as"HFC32"), 25% by weight of pentafluoroethane (thereafter referred to as"HFC125") and 52% by weight of 1,1,1,2-tetrafluoroethane (thereafterreferred to as "HFC134a"), which is considered as the most promisingsubstitute for HCFC22, the composition change thereof caused duringtransfer of the refrigerant from a bomb and like feeding container, toan air-conditioner is a serious problem, since ASHRAE STANDARD (1994)establishes the permissible composition range of HFC32(21-25% byweight), HFC125(23-27% by weight) and HFC134a(50-54% by weight).

As a method to solve the problem, Japanese Unexamined Patent PublicationNo. 157810/1996 proposes a method for allowing the composition to fallwithin the range of the tolerance of the composition by increasing inthe blend composition lower boiling point components beforehand whichare decreased with composition change.

Since a permissible range of performance of refrigerant is usuallywithin ±3% by weight, in particular ±2% by weight with respect to thestandard value, a biased composition concerning lower-boiling-pointcomponents according to the method enlarges differences of performanceof refrigerant from the standard value.

DISCLOSURE OF THE INVENTION

The inventors conducted extensive research on a method for charging aliquid gas so as to solve the problem associated with the compositionchange which occurs when a non-azeotropic blend comprising three typesof liquid gases having different boiling points and stored in a sealedvessel is transferred from a liquid-containing container to anothercontainer.

As a result, the inventors found a method for charging a refrigerantblend characterized in that in case of employing a non-azeotropicmixture comprising 23% by weight of difluoromethane, 25% by weight ofpentafluoroethane and 52% by weight of 1,1,1,2-tetrafluoroethane asrefrigerant, composition change associated with transfer of therefrigerant blend may be allowed to fall within the permissible range ofperformance of refrigerant blend by adjusting a blend composition in abomb and like feeding container to 23.5-25.0% by weight ofdifluoromethane, 23.5-25.0% by weight of pentafluoroethane and50.0-53.0% by weight of 1,1,1,2-tetrafluoroethane, followed bydischarging the refrigerant from the liquid phase at not more than 40°C.

The invention relates to a method for charging a refrigerant blendcharacterized in that in case of employing a non-azeotropic mixturecomprising 23% by weight of difluoromethane, 25% by weight ofpentafluoroethane and 52% by weight of 1,1,1,2-tetrafluoroethane asrefrigerant, composition change associated with transfer of therefrigerant falls within the permissible range of performance ofrefrigerant, by adjusting the blend component in a bomb and like feedingcontainer to about 23.5-25.0% by weight of difluoromethane, about23.5-25.0% by weight of pentafluoroethane and about 50.0-53.0% by weightof 1,1,1,2-tetrafluoroethane, followed by discharging the refrigerantfrom the liquid phase at not more than about 40° C.

In addition, the present invention relates to a method for producing avapor compression refrigerating equipment with a composition range of23% by weight of difluoromethane, 25% by weight of pentafluoroethane and52% by weight of 1,1,1,2-tetrafluoroethane comprising discharging aliquid phase in a feeding container which has a blend composition ofabout 23.5-25.0% by weight of difluoromethane, about 23.5-25.0% byweight of pentafluoroethane and about 50.0-53.0% by weight of1,1,1,2-tetrafluoroethane at not more than about 40° C. and transferringit to a main body of the vapor compression refrigerating equipment.

According to the invention, the temperature during discharge of theliquid phase in feeding container is up to about 40° C., preferablyabout 20-30° C.

According to the production method of the invention, known refrigeratingequipments may be widely used as the main body of vapor compressionrefrigerating equipment.

The non-azeotropic refrigerant blend comprising 23% by weight ofdifluoromethane, 25% by weight of pentafluoroethane and 52% by weight of1,1,1,2-tetrafluoroethane is, in particular, an object of the invention.However, the idea of the invention may be applied to other compositionranges, or, liquid gases of non-azeotropic compositions comprising othercomponents having different boiling points. A blend comprisingdifluoromethane and 1,1,1,2-tetrafluoroethane, and a blend comprisingpentafluoroethane, 1,1,1-trifluoroethane and 1,1,1,2-tetrafluoroethanemay be exemplified.

Examples of the vapor compression refrigerating equipment of theinvention are an air-conditioner, freezer, refrigerator and hot-watersupplier.

Feeding containers according to the present invention are notspecifically limited insofar as the container is a sealed containercapable of storing a refrigerant blend. For example, a bomb isexemplified. As equipments to which a refrigerant blend is transferredand charged, any equipment which utilizes vapor compressionrefrigeration cycle can be used. Said equipments include, but are notspecifically limited to, an air-conditioner, freezer, refrigerator,hot-water supplier, etc.

EXAMPLES

The present invention is illustrated with reference to the followingexamples, but it is to be understood that the invention is not limitedto the examples unless the scope of the invention is departed from.

Example 1 and Comparative example 1

To a 10 liter sealed container, 9 kg of a non-azeotropic mixture ofdifluoromethane (HFC32), pentafluoroethane (HFC125) and1,1,1,2-tetrafluoroethane (HFC134a) having the upper limit composition(25.0/25.0/5 0.0% by weight; example 1) or the lowest limit composition(21.0/25.0/54.0% by weight; comparative example 1) of the permissiblerange with respect to the standard composition (23.0/25.0/52.0% byweight) was charged. The container was placed into a thermostaticchamber in which the temperature was maintained at 10° C. or 40° C.

The mixture from the liquid phase was then transferred to another emptycontainer at a rate of 900 g/min by means of a pump. A portion of thecharging gas was withdrawn through a sampling valve located on acharging pipe near the liquid phase and the composition was analyzed bygas chromatography.

Performance of refrigerant composition at the beginning and end ofcharging was compared under conditions of refrigeration cycle thatevaporating temperature was 0° C.; condensing temperature was 50° C.;overheating and supercooling were 0° C. to determine difference fromstandard composition. The results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Transfer Ratio and Analysis of Collected Gas Composition                                            Coefficient of                                                                        Refrigerating                                                         Performance                                                                           Capacity                                                   HFC        (difference)                                                                          (difference)                                               32 125  134a                                                                             (wt. %)                                                                              KJ/m.sup.3 -                                                                        (wt. %)                                    __________________________________________________________________________    Standard Composition                                                                     23.0                                                                             25.0 52.0                                                                             3.94 (0)                                                                             2947  (0)                                        10° C.                                                                 Upper limit                                                                   beginning  24.9                                                                             24.9 50.2                                                                             3.94 (0)                                                                             3012  (+2.2)                                     end        24.3                                                                             24.4 51.3                                                                             3.94 (0)                                                                             2986  (+1.3)                                     Lowest limit                                                                  beginning  20.9                                                                             24.9 54.2                                                                             3.95 (+0.3)                                                                          2873  (-2.5)                                     end        20.3                                                                             24.4 55.3                                                                             3.95 (+0.3)                                                                          2848  (-3.4)                                     40° C.                                                                 Upper limit                                                                   beginning  24.8                                                                             24.8 50.4                                                                             3.94 (0)                                                                             3007  (+2.0)                                     end        23.6                                                                             23.8 52.6                                                                             3.95 (+0.3)                                                                          2956  (+0.3)                                     Lowest limit                                                                  beginning  20.8                                                                             24.8 54.4                                                                             3.95 (+0.3)                                                                          2869  (-2.6)                                     end        19.6                                                                             23.8 56.6                                                                             3.96 (+0.5)                                                                          2817  (-4.4)                                     __________________________________________________________________________

The refrigerating capacity values of the compositions at the end ofcharging were decreased more than 3% with respect to the standard valueat both 10° C. and 40° C.

Example 2

HFC32/HFC125/HFC134a having a weight ratio of 23.5/23.5/53.0 (the lowestlimit) was transferred.

The conditions of transfer were the same as those of example 1 exceptthat temperature of thermostatic chamber was 40° C. which was the worstcondition. The results are shown in table 2.

Example 3

Performance of refrigerant composition of example 2 charged at 40° C.was compared under conditions of refrigeration cycle that evaporatingtemperature was 0° C.; condensing temperature was 50° C.; overheatingand supercooling were 0° C. The results of example 3 together with theresults of example 2 are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Transfer Ratio and Analysis of Collected Gas Composition                                            Coefficient of                                                                        Refrigerating                                                         Performance                                                                           Capacity                                                   HFC        (difference)                                                                          (difference)                                               32 125  134a                                                                             (wt. %)                                                                              KJ/m.sup.3 -                                                                        (wt. %)                                    __________________________________________________________________________    Standard Composition                                                                     23.0                                                                             25.0 52.0                                                                             3.94 (0)                                                                             2947  (0)                                        Example 2                                                                     lowest limit                                                                  beginning  23.3                                                                             23.4 53.3                                                                             3.95 (+0.3)                                                                          2941  (-0.2)                                     end        22.1                                                                             22.4 55.5                                                                             3.97 (+0.8)                                                                          2889  (-2.0)                                     __________________________________________________________________________

Composition change associated with transfer of non-azeotropicHFC32/HFC125/HFC134a refrigerant blend used as a working fluid for vaporcompression refrigeration cycle may be allowed to fall within thepermissible range (±3% by weight, preferably ±2% by weight) ofperformance of refrigerant (coefficient of performance, refrigeratingcapacity), whereby a significant change in performances and an increasein flammability of refrigerant can be prevented.

What is claimed is:
 1. A method for charging a refrigerant blendcharacterized in that, in case of employing as refrigerant anon-azeotropic blend comprising 23% by weight of difluoromethane, 25% byweight of pentafluoroethane and 52% of 1,1,1,2-tetrafluoroethane,composition change associated with transfer is allow to fall within thepermissible range of performance of the non-azeotropic refrigerant blendby adjusting a composition of the non-azeotropic blend in a feedingcontainer such as bomb to 23.5-25.0% by weight of difluoromethane,23.5-25.0% by weight of pentafluoroethane and 50.0-53.0% by weight of1,1,1,2-tetrafluoroethane followed by discharging the non-azeotropicblend from a liquid phase at 40° C. or less.
 2. The method for charginga refrigerant blend according to claim 1 wherein the composition changeassociated with the transfer is allowed to fall within ±3% by weight ofperformance of the non-azeotropic refrigerant blend.
 3. A method forproducing a vapor compression refrigerating equipment with a compositionrange of 23% by weight of difluoromethane, 25% by weight ofpentafluoroethane and 52% by weight of 1,1,1,2-tetrafluoroethanecomprising discharging a liquid phase in a feeding container with ablend composition of 23.5-25.0% by weight of difluoromethane,23.5-25.0by weight of pentafluoroethane and 50.0-53.0% by weight of1,1,1,2-tetrafluoroethane at not more than 40° C. and transferring it toa main body of the vapor compression refrigerating equipment.